For a variety of reasons, for example, accurate measurement of fluid flow through a conduit or pipeline, such as an irrigation water pipeline, it is desirable that the fluid flowing through the conduit have a substantially flat face velocity profile of maximum mean flow diameter, i.e., a diameter approaching or approximating the inner diameter of the conduit.
Frequently, departures from the optimum occur. The velocity profile maybe become convex or concave, or asymmetrical, or symmetrical but non-uniform, or the flow may develop a swirl, e.g., a helical or corkscrew flow pattern. A turn, curve or elbow in a pipeline may impart a swirl to the fluid; or a valve or impediment in the conduit through which or around which the fluid is required to flow may distort the flow and cause the flow to become irregular and unstable.
Distortions and instabilities introduced into the flow will persist for a distance equal to several pipe diameters, customarily as many as 10 to 30 pipe diameters, downstream from the cause of the disturbance. Consequently, many flow meters and systems for measuring fluid flow require a long straight run of pipe both upstream and downstream from the point of measurement to provide a reasonable degree of flow stability at the point of flow measurement.
Flow straighteners are employed to convert unstable and problematic fluid flow conditions to more stable and consistent flow conditions. Conventional flow straighteners consist of a bundle of elongate tubes, or a plurality of circumferentially spaced longitudinally extending vanes, filling the conduit adjacent or downstream from the point of disturbance.
In some instances, the flow straightener may be combined with a flow measuring system. For example, see U.S. Pat. No. 3,049,009 for a disclosure of flow straightening vanes combined with and conformed to the front face of an impeller type rotary flow meter, and U.S. Pat. No. 5,363,699 for flow stabilizing and conditioning apparatus located upstream from apparatus for determining a characteristic of the fluid flow.
The flow straightening, conditioning and stabilizing apparatus of U.S. Pat. No. 5,363,699 is predicated on and embodies the technology of the fluid flow meters disclosed in U.S. Pat. No. 4,638,672 and the fluid mixing or dispersing device disclosed in U.S. Pat. No. 4,812,049, all of which patents are owned by the assignee of the present invention. Fluid flow meters and static mixers embodying the patented device are made and sold by the assignee of this invention, McCrometer, Inc., of Hemet, Calif., under the Registered Trademark “V-CONE”.
The V-CONE devices are characterized by a flow displacement member positioned coaxially within a conduit or pipe and comprised of two conical frustums facing respectively in the upstream and downstream directions and joined at their larger ends.
As described in U.S. Pat. No. 5,363,699, the V-CONE device, with and without swirl mitigating vanes, is employed for converting unstable, distorted and/or non-uniform fluid flows to optimum flow conditions, i.e., an essentially uniform, consistent and symmetrical flow pattern having a flat face velocity profile and a large and axially centered mean flow diameter.
It would be desirable to embody these advantageous characteristics into a more economical and more conveniently installed flow straightener.